1. Field of the Invention
The present invention relates to electronic packaging. More particularly, the present invention relates to electronic interposers used in electronic packaging to make electrical connection of electronic modules to printed wiring boards, and the like.
2. Background and Related Art
Compression connectors, such as those employed in land grid array (LGA) connections, are well known in the art. Typical LGA compression connections employ an interposer to connect a single chip or multiple chip module (MCM) to a printed wiring board (PWB). The MCM generally comprises multiple integrated circuits or chips assembled into a subsystem the size of traditional single chip packages. The single chip or MCM may be connected to the PWB through the interposer with the chip module circuit pads making contact with the array of connection points extending from one surface of the interposer and the PWB circuit pads making contact with the array of connections extending from the other surface of the interposer. Compression forces are employed to hold the chip module and PWB against the interposer.
Various forms of interposers have been designed to facilitate the LGA connection of the single chip or MCM to the PWB. One of the considerations in designing interposers is to create a structure that will accommodate the thermal mismatch between chip module and PWB. Another consideration in designing interposers is to create a structure that will accommodate differences in topography between the mating surface profiles and mating conductor of the chip module and PWB.
Interposer layers of both substantially rigid and relatively resilient insulating materials have been employed for this purpose. In using such materials, a variety of conductor interconnect structures have been employed in the prior art to electrically connect the contacts or pads on one surface of the interposer to the corresponding contacts or pads on the other surface of the interposer. One form of conductor interconnect structure employed is designed to be resilient or deformable. As such, the deformable conductor can move to accommodate, for example, the CTE dimensional mismatch between the chip module and PWB.
One example of a resilient or deformable conductor used in rigid or semi-rigid layers of insulating material is the resilient wadded-wire connector, sometimes also known as the “fuzz-button” type connector or the connector made by CINCH Connectors, Inc. under the trademark CIN::APSE. An example of such type of connector is found in U.S. Pat. No. 6,386,890. The interposer in such arrangements typically comprises a substantially rigid interposer layer of plastic having a plurality or array of apertures with each aperture further having disposed thereon a deformable, randomly configured, resilient conductor material for connecting a MCM, for example, to a PWB. The resilient conductors of wadded wire are typically held by friction within a plastic layer.
Such wadded-wire button or connector arrangements have proven to be reliable once assembled but have been found somewhat difficult to handle beforehand without causing damage to, or displacement of, the wadded-wire button connector. Contact with the wadded-wire button connectors in handling may result in missing button connectors or pulled/smeared button connectors. Since the connectors are typically retained in the interposer layer by friction, they are prone to being pushed or pulled from position. In addition, handling may result in smearing a button connector wherein handling contact with the connector causes a portion of the wadded-wire to become unwadded and free of the aperture wherein it may extend across the surface of the interposer material and short to the wadded-wire button connector of an adjacent aperture.
FIG. 1 depicts an example of a typical wadded-wire button connector arrangement which, as can be seen, is randomly wound. An array of nine such connectors is shown to illustrate the connector arrangement but it is understood that, in practice, the array of connectors would typically be made much greater. As shown in FIG. 1A, wadded-wire connectors 1 are held by friction in apertures 3 in insulating layer 5. As shown in FIG. 1B, the wire of button connector 1 has been smeared to unwind portion 7 such that it could short to an adjacent wadded wire button connector.